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Old 08-08-2020, 11:02 AM   #1
Zender
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Default Power good problem in PSU all voltages seems to be OK

Hi there I just got some Cooler Master mpx-7001-acabw-eu PSU. There is sticker on it so it is not been open ever.

It have some power good problem, all voltages seems to be ok, but that PG is 0 and blinking on this simple PSU tester, also when on this tester a PSU let out some strange sound inside it ( I can't record it since PSU tester is whistle and covering that sound from PSU ).
When I try to connect a green and black wire on 24 pin connector a fan on PSU just little move and nothing.

Here is a video of problem : https://www.youtube.com/watch?v=3cmO8x05lA4


Question is, like I see voltages are good and only problem is this PG, so does this can be fix easily and PSU will work without problems after that ?
My skills are only to replace a broken capacitor, and from what I see here that fan try to start and move a little, it like have no enought power to start and that looks like to me, that some of capacitors is out...
What do you think is this worth a try and if I open it can someone tell me which capacitor to look out since I'm not good to find a problem, only if it is capacitor physically visible that is broken.
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Old 08-08-2020, 11:32 AM   #2
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Default Re: Power good problem in PSU all voltages seems to be OK

post a pic of the underside of the board,
there was a psu that was known for this problem that was on russian forums a lot - had a shorted capacitor or diode or something on the underside of the pcb
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Old 08-08-2020, 12:10 PM   #3
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Default Re: Power good problem in PSU all voltages seems to be OK

Ok, I open it up.

From top side I dont see any kind of problem that I can spot with the eyes, except this big capacitor 400v 470uf that have hump on the center ( it is not flat ).

And from bottom side only what I can spot is that there can be some problem in marked area.
















So capacitor is probably out, but if something else can be problem here ?
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Old 08-08-2020, 01:28 PM   #4
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Default Re: Power good problem in PSU all voltages seems to be OK

the big cap is probably just the plastic cover sticking up - simple test is to press down on it.
the arrow in your last pic is flux from resoldering - look above it around the 8pin chip though - that's an interesting area in the photo
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Old 08-08-2020, 02:36 PM   #5
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Default Re: Power good problem in PSU all voltages seems to be OK

I get a very hard pressure on it and it remain hump on center, it simply can't go down.

And I'm pretty sure that I'm firt who open this PSU, so that arrowed problem can be only if something melted there.

I desolder a big one since I have doubts about him, and I measure only 1.7 nF on it..

I don't know does this device can measure correctly a capacity on this kind of very big capacitor.

As picture shows I took one new 25V 1000 uF and do measurements are good, so if this device have ability that can measure this big one, then he is faulty and need replacement ?




I also read this on internet : ''PG problem can be due to bad main filter cap, secondary side PWM IC and corresponding components like open resistor, bad caps and leaky diodes. All components related to the PG line can be a suspect.''

Where is exactly PG line and what to check more ?
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Old 08-08-2020, 04:23 PM   #6
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Default Re: Power good problem in PSU all voltages seems to be OK

PG = "Power good" line and is exactly what your tester is indicating that isn't transitioning.
IIRC it's the gray wire in the standard ATX color scheme.

I had a deer psu that failed with power good problems, it turned out a little ceramic capacitor shorted out, causing PG to never rise. Fix was simply to replace the little 0.001F ceramic capacitor, until deer raised its ugly head again with a different problem...
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Old 08-08-2020, 06:07 PM   #7
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Default Re: Power good problem in PSU all voltages seems to be OK

Ok, so I need to check from other side of board all of capacitors for shorts ?
And to replace this big on which is probably dead ?
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Old 08-08-2020, 08:51 PM   #8
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Default Re: Power good problem in PSU all voltages seems to be OK

Well, it's an idea, who knows what's wrong with your particular PSU -- it was what was ailing my deer...
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Old 08-09-2020, 05:40 PM   #9
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Default Re: Power good problem in PSU all voltages seems to be OK

I will buy this big capacitor 400v 470uf, replace it then I will try. I'm convinced the problem lies there.
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